482 Geological Society. 



the second oldest known example of the Lyssakina. Some remarks 

 were added on the mineral state of the spicules and their association 

 with chert. The author proposed for it the name of Astroconia 

 Granti., the former in allusion to the peculiarly spinose character of 

 the rays of the sexradiate spicules. The anchoring spicules were 

 described as consisting of a straight shaft with four recurved rays, 

 each having a small bifid spine near the base on the outer surface. 



In the discussion which followed 



Prof. Duncan said it was interesting to see the modern Hexacti- 

 nellids thus foreshadowed. Very lately he had seen one of the 

 spicular forms described by Prof. Sollas in a form he had just 

 described. Ho quite agreed with the author in assigning this form 

 to the Lyssakine HexactineUids. There coiild be no question as to 

 the solution of sponge-spicules in sea-water, as he had lately seen 

 evidence in specimens of deep-sea dredgings. The results of Mr. 

 Maw's washing promised to be very interesting. He had examined 

 many, but had not yet found either sponge-spicules or Foraminifera. 



Prof. lluPERT Jones noticed that there are different kinds of 

 " chert," and expressed his opinion that Mr. Sollas had well ex- 

 plained the origin and formation of the spicular strata which he 

 had described on this and other occasions. He thought that Dr. 

 Wallich's hypothesis of the conversion of extensive layers of sponge- 

 protoplasm into black flint elucidated many, but not all, of the 

 phenomena connected with the origin of such siliceous strata as flint 

 and chert. He noticed that sponge-spicules, and numerous other 

 Microzoa from the Upper Silurian shales of Shropshire, had been 

 noticed lately by Mr. Smith of Kilwinning. 



Dr. Hicks said that it was remarkable that chert was not asso- 

 ciated with Protosjoongia, as, on either Dr. Wallich's or Prof. Sollas 's 

 view, might have been expected. 



Prof. JuDD said that as the solution of sUiceous organisms had 

 been recently doubted. Prof. SoUas's observations were of additional 

 interest. He himself fiilly believed that this solution did take 

 place ; now and then he had found, in examining the residues left 

 by dissolving chalk in acid, the thickest portions of siliceous spicules 

 stiU remaining not quite destroyed in chalk. 



Prof. Sollas replied that he believed a spicule had been described 

 by Mr. Carter similar to that mentioned by Prof. Duncan. The one 

 described now by him was, however, much more robust. He had 

 never been able to find spicules in the Wenlock. He really could 

 not comprehend what Dr. Wallich's views really were. That none 

 of the fossil siliceous spicules which the author had described were 

 originally calcareous was quite certain. As for Protospongia, it 

 did not occur in limestone, and bore a very small proportion to the 

 mass of the bed ; and this might account for the absence of the 

 chert. 



